Massive volcanic eruptions that produced ash clouds wiped out nearly 95% of life on sea and 70% on land.
"This could literally be the smoking gun that explains the latest Permian extinction," says Steve Grasby, adjunct professor in geoscience at University of Calgary, the journal
"Our research is the first to show direct evidence that massive volcanic eruptions - the largest the world has ever witnessed - caused massive coal combustion, thus supporting models for significant generation of greenhouse gases at this time," says Grasby who led the study.
Grasby and colleagues discovered layers of coal ash in rocks from the extinction boundary in Canada's High Arctic that give the first direct proof to support this, according to a Calgary statement.
Unlike end of dinosaurs, 65 million years ago, where there is widespread belief that the impact of a meteorite was at least the partial cause, it is unclear what caused the late Permian extinction.
Previous researchers have suggested massive volcanic eruptions through coal beds in Siberia would generate significant greenhouse gases causing runaway global warming.
At the time of the extinction, the Earth contained one big land mass, a supercontinent known as Pangaea.
The environment ranged from desert to lush forest. Four-limbed vertebrates were becoming more diverse and among them were primitive amphibians, early reptiles and synapsids - the group that would, one day, include mammals.